Add failing test

Author: ankurdave

graphx/src/test/scala/org/apache/spark/graphx/GraphSuite.scala

@@ -159,6 +159,31 @@ class GraphSuite extends FunSuite with LocalSparkContext {
     }
   }
 
+  test("mapVertices changing type with same erased type") {
+    withSpark { sc =>
+      val vertices = sc.parallelize(Array[(Long, Option[java.lang.Integer])](
+        (1L, Some(1)),
+        (2L, Some(2)),
+        (3L, Some(3))
+      ))
+      val edges = sc.parallelize(Array(
+        Edge(1L, 2L, 0),
+        Edge(2L, 3L, 0),
+        Edge(3L, 1L, 0)
+      ))
+      val graph0 = Graph(vertices, edges)
+      // Trigger initial vertex replication
+      graph0.triplets.foreach(x => {})
+      // Change type of replicated vertices, but conserve erased type
+      val graph1 = graph0.mapVertices {
+        case (vid, integerOpt) => integerOpt.map((x: java.lang.Integer) => (x.toDouble): java.lang.Double)
+      }
+      // Access replicated vertices, exposing the erased type
+      val graph2 = graph1.mapTriplets(t => t.srcAttr.get)
+      assert(graph2.edges.map(_.attr).collect.toSet === Set[java.lang.Double](1.0, 2.0, 3.0))
+    }
+  }
+
   test("mapEdges") {
     withSpark { sc =>
       val n = 3